2013 Road Bike Gear

Knowledge Is Power

Rotor’s Power crank puts a power meter in each crankarm to give you more detailed information

matt phillips

(Photo by Rotor’s Power meters add just 30 grams to the 3D+ crank. (Matt Phillips))

The exploding popularity of training with power brings with it a rush of products to fill the demand. Rotor’s distinctive crankarms have been a popular building block for SRM, Power2Max, and Quarq’s power-meter systems. Now the Spanish company is jumping into the arena with a power meter of its own, featuring independent left and right sensors.

The Power crank is based on the company’s 3D+ cranks. Essentially, Rotor drops four strain gauges (eight total) into existing lengthwise weight-relieving drillings in each 3D arm. Atop each arm is an ANT+ transmitter and battery (a commonly available and user-replaceable CR2477).

The benefit of the system—independent left- and right-side power meters—is more precise information. Instead of averaging left- and right-leg power data together as some other meters do, a dual system shows the power each leg produces, so the rider can recognize and correct any imbalances. (With a firmware update, compatible Garmin computers will display individual left/right data.) Additionally, the system will reveal energy-wasting inefficiencies with pushing back on the driving leg.

The system is light, adding only about 30 grams to Rotor’s 3D+crankset, and it’s offered in either mountain or road double-ring configurations. The Power’s stock spider is Rotor’s MAS (Micro Adjust Spider) which, when used with Rotor’s ovalized chainrings, allows more fine-tuning of the ring’s position. By adjusting the clocking of an oval ring, the rider can control when the tall section of the ring hits the pedal stoke. MAS cuts the adjustment increments in half, from 5 degrees to 2.5, giving the rider more control of the feel of the pedal stroke. Nerdy, for sure, but if you’re the kind of rider who’s interested in independent left/right power and ovalized rings, you’ll love it.

Another claimed benefit of Rotor’s design: Because the strain gauges are in the arm, and not the spider, it is not necessary to recalibrate if you change chainrings, and the precision is not affected by improper chainring-bolt torque.

For easy compatibility with most of the myriad bottom-bracket systems out there, the Power crank uses a long, 30mm-diameter aluminum axle. Frame compatibility is handled by Rotor’s impressive array of adapter bottom brackets: You won’t need a new set of cranks when you purchase that new frame, just a new bottom bracket. It’s nice to know that your $2,300 power-meter cranks will likely be compatible with your next frame. Frames that use the BB90 standard, which includes many recent Trek bikes, are an exception.

Rotor’s Power crank will be available in February 2013 for $2,300, without rings. Initial lengths offered will be 170-, 172.5- and 175mm, though the company expects to offer more options in the future.